Evidence of Explosive Evaporation in a Microflare Observed by Hinode/EIS

TL;DR

This study provides observational evidence of explosive chromospheric evaporation during a microflare, showing temperature-dependent plasma flows consistent with flare models involving nonthermal electron beams.

Contribution

First detailed observation of explosive evaporation in a microflare, confirming that similar dynamic processes occur across different flare magnitudes.

Findings

Temperature-dependent upflows and downflows observed

Line intensities and widths correlated with evaporation

Results align with numerical flare simulations

Abstract

We present a detailed study of explosive chromospheric evaporation during a microflare which occurred on 2007 December 7 as observed with the EUV Imaging Spectrometer (EIS) onboard Hinode. We find temperature-dependent upflows for lines formed from 1.0 to 2.5 MK and downflows for lines formed from 0.05 to 0.63 MK in the impulsive phase of the flare. Both the line intensity and the nonthermal line width appear enhanced in most of the lines and are temporally correlated with the time when significant evaporation was observed. Our results are consistent with the numerical simulations of flare models, which take into account a strong nonthermal electron beam in producing the explosive chromospheric evaporation. The explosive evaporation observed in this microflare implies that the same dynamic processes may exist in events with very different magnitudes.